After the troops detained the suspect, and while they were searching the house, “the force was attacked by a hand grenade from one of the neighboring houses, prompting a quick response, and then the forces pulled back to their headquarters,” the Joint Operations Command said.

The joint command statement said Iraqi forces on the ground called in air support when they saw the police, believing them to be “a group of gunmen gathering without coordination with the assigned force.”

Obaidi said an airstrike hit the gathering, killing the six police officers and wounding 20 others, including security officers, the mayor and town’s police chief.

“We demand Iraqi government to investigate the attack and give an explanation on why such operation was conducted without informing local authorities,” Obaidi said.

“Those security officers who were killed in the airstrikes had fought ISIS militants before,” al-Obaidi added.

Col. Ryan Dillon, a US Army spokesman for the Combined Joint Task Force, said the incident is under investigation but US warplanes give support when requested and approved by the Iraqi military.

A US military official told CNN they are still investigating to see whether there were US aircraft in the area at the time.

Al-Baghdadi, about 200 km (125 miles) northwest of Baghdad, is the closest village to the Al Asad Air Base, where the US military has planes.

Al-Baghdadi was mostly under ISIS control in 2015 for a few weeks before being was liberated.